linux-kernel - Re: [RFC v0 7/8] Input: ims-pcu: use firmware

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Date:	Wed, 3 Aug 2016 00:42:14 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	"Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:	Daniel Wagner <daniel.wagner@...-carit.de>,
	Arend van Spriel <arend.vanspriel@...adcom.com>,
	Bjorn Andersson <bjorn.andersson@...aro.org>,
	Daniel Wagner <wagi@...om.org>,
	Bastien Nocera <hadess@...ess.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Johannes Berg <johannes.berg@...el.com>,
	Kalle Valo <kvalo@...eaurora.org>,
	Ohad Ben-Cohen <ohad@...ery.com>,
	Mimi Zohar <zohar@...ux.vnet.ibm.com>,
	David Howells <dhowells@...hat.com>,
	Andy Lutomirski <luto@...capital.net>,
	David Woodhouse <dwmw2@...radead.org>,
	Julia Lawall <julia.lawall@...6.fr>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
	linux-kselftest@...r.kernel.org,
	linux-wireless <linux-wireless@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [RFC v0 7/8] Input: ims-pcu: use firmware_stat instead of completion

On Tue, Aug 2, 2016 at 12:41 AM, Luis R. Rodriguez <mcgrof@...nel.org> wrote:
> On Tue, Aug 02, 2016 at 08:53:55AM +0200, Daniel Wagner wrote:
>> On 08/02/2016 08:34 AM, Luis R. Rodriguez wrote:
>> >On Tue, Aug 02, 2016 at 07:49:19AM +0200, Daniel Wagner wrote:
>> >>>The sysdata API's main goal rather is to provide a flexible API first,
>> >>>compartamentalizing the usermode helper was secondary. But now it seems
>> >>>I may just also add devm support too to help simplify code further.
>> >>
>> >>I missed the point that you plan to add usermode helper support to
>> >>the sysdata API.
>> >
>> >I had no such plans, when I have asked folks so far about "hey are you
>> >really in need for it, OK what for? " and "what extended uses do you
>> >envision?" so I far I have not gotten any replies at all. So -- instead
>> >sysdata currently ignores it.
>>
>> So you argue for the remoteproc use case with 100+ MB firmware that
>> if there is a way to load after pivot_root() (or other additional
>> firmware partition shows up) then there is no need at all for
>> usermode helper?
>
> No, I'm saying I'd like to hear valid uses cases for the usermode helper and so
> far I have only found using coccinelle grammar 2 explicit users, that's it. My
> patch series (not yet merge) then annotates these as valid as I've verified
> through their documentation they have some quirky requirement.

In certain configurations (embedded) people do not want to use
initramfs nor modules nor embed firmware into the kernel. In this case
usermode helper + firmware calss timeout handling provides necessary
wait for the root filesystem to be mounted.

If we solve waiting for rootfs (or something else that may contain
firmware) then these cases will not need to use usermode helper.

Thanks.

-- 
Dmitry